The present invention relates to image processing methods, image processing apparatuses, and data recording media and, more particularly, to image processing methods, image processing apparatuses, and data recording media in which, in variable-length coding of frequency components of an interlaced image signal, a sequence of the frequency components is adaptively rearranged, thereby improving coding efficiency.
In recent years, discrete cosine transformation (DCT) has been widely utilized in image coding processing. In MPEG as a representative image coding method, an input image signal is divided correspondingly to plural rectangular blocks constituting a single display screen as units of DCT processing, and DCT processing is performed block by block to the blocked image signal.
A specific description is given of image coding in MPEG.
FIG. 26 is a block diagram illustrating a construction of a conventional image processing apparatus which performs the above-mentioned image coding. In FIG. 26, reference numeral 200a designates a conventional image processing apparatus (image coding apparatus), which performs coding including DCT processing to an image signal. This image coding apparatus 200a consists of a blocking unit 102 for dividing an input image signal 101 correspondingly to plural blocks constituting a single display screen to generate an image signal (plural pixel values) 103 corresponding to each block, a DCT unit 104 for performing DCT processing to the image signal (pixel values) 103 to transform the image signal (pixel values) 103 into frequency components (DCT coefficients) 105, and a quantization unit 106 for quantizing the output 105 of the DCT unit 104 to generate quantized values 107 corresponding to each block. Herein, the DCT unit 104 and the quantization unit 106 constitute an information source coding unit 200a1.
Further, the image coding apparatus 200a consists of a scanner 109 for setting the processing order for coding the quantized values 107, and a variable-length coding unit (hereinafter referred to as a VLC unit) 112 for performing variable-length coding to quantized values 111 to which the processing order has been set, according to the set order, to generate a bit stream 113 corresponding to the image signal of each block.
A description is given of the operation.
Initially, the blocking unit 102 blocks an input image signal 101 correspondingly to rectangular blocks each comprising 8xc3x978 pixels, and outputs an image signal (plural pixel values) 103 corresponding to each block. The DCT unit 104 transforms the image signal (pixel values) 103 into plural frequency components (DCT coefficients) 105 by DCT. The quantization unit 106 converts the DCT coefficients 105 into quantized values 107 by quantization.
Then, the scanner 109 performs rearrangement of the quantized values 107 so as to improve the efficiency of variable-length coding. That is, the scanner 109 sets the processing order for coding. Thereafter, the VLC unit 112 performs variable-length coding to the quantized values which have been rearranged, according to the set order. In addition, run length coding is used in variable-length coding processing. Therefore, when a scan is performed so that coefficients of about the same size are consecutive, the efficiency of variable-length coding is improved.
In coding an interlaced image signal, when correlations between adjacent scan lines are strong, frame DCT processing, i.e., DCT using a frame as a unit, is carried out. When correlations between scan lines in a field are strong, field DCT processing, i.e., DCT using a field as a unit, is carried out.
More specifically, as shown in FIG. 27, in frame DCT processing of an interlaced image signal, scan lines of a first field and scan lines of a second field are alternately arranged to form one frame-screen. This frame screen is divided into plural macroblocks each comprising 16xc3x9716 pixels. Each macroblock is divided into four subblocks-each comprising 8xc3x978 pixels. Thereby, the image signal is subjected to DCT processing subblock by subblock. Meanwhile, in field DCT processing of an interlaced image signal, Each of macroblocks constituting one frame screen is formed by two first subblocks comprising only scan lines of a first field and two second subblocks comprising only scan lines of a second field. Thereby, the image signal is subjected to DCT processing subblock by subblock.
In MPEG, frame DCT or field DCT is adaptively selected for each macroblock. Accordingly, in order to perform accurate decoding to an input image signal, the blocking unit 102 in the image coding apparatus 200a outputs DCT processing information 114 indicating a unit of DCT processing for each macroblock (that is, information indicating whether each macroblock has been subjected to frame DCT or field DCT), together with the blocked image signal. Since a subblock which has been subjected to field DCT (a field DCT block) comprises only odd scan lines or only even scan lines among scan lines constituting one frame screen, a DCT coefficient group corresponding to the field DCT block includes more DCT coefficients indicating that the rate of change of pixel values in a vertical direction of a display screen is higher, as compared with a DCT coefficient group corresponding to a subblock which has been subjected to frame DCT (a field DCT block).
FIG. 28 is a block diagram illustrating a construction of an image decoding apparatus corresponding to the image coding apparatus shown in FIG. 26. In FIG. 28, reference numeral 200b designates an image processing apparatus (image decoding apparatus), which decodes the coded image signal 113 which has been coded by the image coding apparatus 200a. This image decoding apparatus 200b consists of a variable-length decoding unit (hereinafter referred to as a VLD unit) 201 for performing variable-length decoding to the coded image signal 113, and an inverse scanner 202 for performing an inverse scan to quantized values 111 which are obtained by decoding so that the order of the quantized values 111 is returned to the order before rearrangement in coding. Further, the image decoding apparatus 200b consists of an inverse quantization unit 203 for inverse-quantizing quantized values 107 which have been subjected to inverse scanning, to generate DCT coefficients (frequency components) 105 corresponding to a decoding target block to be subjected to decoding, an inverse DCT unit 204 for performing inverse DCT processing to the DCT coefficients 105 to generate an image signal (pixel values) 103 corresponding to the decoding target block, and an inverse blocking unit 205 for inverse-blocking the image signals 103 on the basis of the DCT processing information 114 from the image coding apparatus 200a, thereby regenerating an image signal 101 corresponding to one frame screen. Herein, the inverse quantization unit 203 and the inverse DCT unit 204 constitute an information source decoding unit 200b1.
In the image decoding apparatus 200b, inverse converting processes corresponding to the respective converting processes in the image coding apparatus 200a are carried out to a coded image signal, in the reverse order of the order in coding, thereby accurately decoding the coded image signal.
FIG. 29 is a block diagram illustrating a construction of another conventional image coding apparatus.
In FIG. 29, reference numeral 200c designates an image processing apparatus (image coding apparatus), which performs intra-frame predictive coding processing comprising generating predicted values of quantized values of a coding target block using information in a frame, and coding difference values between the predicted values and the quantized values of the coding target block.
This image coding apparatus 200c includes the image coding apparatus 200a, a prediction unit 200c2 for generating predicted values, and a scanning unit 200c1 for changing a scan method using a parameter concerning generation of the predicted values. The prediction unit 200c2 consists of a predictor 305 for generating predicted values 303, and outputting first prediction information 309a and second prediction information 309b concerning generation of the predicted values, an adder 301 for subtracting the output (predicted values) 303 of the predictor 305 from the output 107 of the quantization unit 106, and an adder 304 for adding the output 303 of the predictor 305 to an output 302 of the adder 301.
The scanning unit 200c1 consists of three scanners 109s1xcx9c109s3 having different scan methods, for scanning the output 302 of the prediction unit 200c2, a first switch 108c for selecting one of the three scanners on the basis of a control signal 116 and supplying the output 302 of the prediction unit 200c2 to the selected scanner, a second switch 110c for selecting one of the three scanners on the basis of the control signal 116 and supplying an output of the selected scanner to the VLC unit 112, and a scan control unit 1401c for generating the control signal 116 on the basis of the first prediction information 309a. In addition, the second prediction information 309b is output from the image coding apparatus 200c. 
In the image coding apparatus 200c thus constructed, a scan method is changed using the parameter concerning generation of predicted values (prediction information) 309, whereby the efficiency of variable-length coding is enhanced.
A description is given of a method for generating predicted values with reference to FIG. 30.
FIG. 30 shows a macroblock comprising 16xc3x9716 pixels. This macroblock comprises four subblocks (hereinafter simply referred to as blocks) R0, R1, R2 and X each comprising 8xc3x978 pixels. The block X is a coding target block, and the blocks R0, R1 and R2 are already coded blocks which are adjacent to the coding target block X. Either block R1 or block R2 is referred in generating predicted values (quantized values) of the coding target block X. The block to be referred is decided using DC coefficients of the blocks R0, R1 and R2 (quantized values at the left upper ends of these blocks). Specifically, the absolute value of the difference between the DC coefficients of the blocks R0 and R1 is compared with the absolute value of the difference between the DC coefficients of the blocks R0 and R2. When the absolute value of the difference between the DC coefficients of the blocks R0 and R1 is larger, the block R1 is referred (reference in a vertical direction). When it is smaller, the block R2 is referred (reference in a horizontal direction).
When the block R1 is referred, the DC coefficient (the quantized value at the left upper end) of the block R1 and AC coefficients (quantized values at the uppermost line, except the DC coefficient) of the block R1 are used as predicted values of the coefficients of the block X at the same positions. When the block R2 is referred, the DC coefficient (the quantized value at the left upper end) of the block R2 and AC coefficients (quantized values at the leftmost line, except the DC coefficient) of the block R2 are used as predicted values of the coefficients of the block X at the same positions. In addition, in a case where the efficiency of variable-length coding is degraded by predicting AC coefficients, no AC prediction may be carried out.
A scan method is changed according to ON/OFF of Ac prediction (whether AC prediction is performed or not) in intra-frame prediction. Further, when AC prediction is in the ON state, a scan method is changed according to a reference direction of prediction. The first prediction information 309a supplied to the scan control unit 1401c includes ON/OFF information indicating ON/OFF of AC prediction, and prediction direction information indicating a reference direction for AC prediction, and the second prediction information 309b includes only the ON/OFF information of AC prediction.
When Ac prediction is in the OFF state, a scan of quantized values is executed in the order shown in FIG. 31(a). Thereby, the processing order for coding is set to the quantized values. In this case, in a group of quantized values corresponding to a subblock, high-frequency components uniformly distribute in vertical and horizontal directions very often. Therefore, the quantized values are uniformly scanned in the order from low-frequency components to high-frequency components. When AC prediction is performed and a vertical direction is referred, a scan of quantized values is executed in the order shown in FIG. 31(b). In this case, a group of quantized values corresponding to a subblock has a distribution in which high-frequency components in a horizontal direction are reduced by the prediction. Therefore, the quantized values are scanned with a priority given to a horizontal direction, thereby improving the efficiency of variable-length coding. When AC prediction is performed and a horizontal direction is referred, a scan of quantized values is executed in the order shown in FIG. 31(c). In this case, a group of quantized values corresponding to a subblock has a distribution in which high-frequency components in a vertical direction are reduced by the prediction. Therefore, the quantized values are scanned with a priority given to a vertical direction, thereby improving the efficiency of variable-length coding.
FIG. 32 is a block diagram illustrating a construction of an image decoding apparatus corresponding to the image coding apparatus shown in FIG. 29. In FIG. 32, reference numeral 200d designates an image processing apparatus (image decoding apparatus), which decodes the coded image signal 308 that has been coded in the image coding apparatus 200c. 
This image decoding apparatus 200d has an inverse scanning unit 200d1 for performing an inverse scan to quantized values which are obtained by variable-length decoding of the coded image signal 308 so that the order of the quantized values is returned to the order before scanning in coding, and changing an inverse scan method on the basis of the prediction information (parameter) concerning generation of predicted values in the image coding apparatus 200c, and a prediction unit 200d2 for adding quantized values (predicted values) of a decoding target block which are predicted from quantized values of an already decoded block in the vicinity of the decoding target block, to the quantized values corresponding to the decoding target block which have been subjected to inverse scanning.
The inverse scanning unit 200d1 consists of three inverse scanners 202s1xcx9c202s3 having different inverse scan methods, for inverse-scanning the output of the VLD unit 201, a first switch 108d for selecting one of the three inverse scanners on the basis of a control signal 116 and supplying the output of the VLD unit 201 to the selected inverse scanner, a second switch 110d for selecting one of the three inverse scanners on the basis of the control signal 116 and supplying the output of the selected inverse scanner to the prediction unit 200d2, and an inverse scan control unit 1401d for generating the control signal 116 on the basis of the first prediction information 309a. 
In addition, the inverse scanner 202s1 performs an inverse scan corresponding to the scan by the scanner 109s1 in the image coding apparatus 200c, the inverse scanner 202s2 performs an inverse scan corresponding to the scan by the scanner 109s2 in the image coding apparatus 200c, and the inverse scanner 202s3 performs an inverse scan corresponding to the scan by the scanner 109s3 in the image coding apparatus 200c. 
The prediction unit 200d2 consists of a predictor 401 for generating predicted values 303 on the basis of the second prediction information 309b output from the image coding apparatus 200c and values 107d corresponding to the quantized values 107 in the image coding apparatus 200c, and generating control prediction information 309axe2x80x2 corresponding to the first prediction information 309a in the image coding apparatus 200c, and an adder 304 for adding the predicted values 303 to the output 302 of the inverse scanning unit 200d1. In addition, like the first prediction information 309a, the control prediction information 309axe2x80x2 includes ON/OFF information of AC prediction and prediction direction information of AC prediction.
In the image decoding apparatus 200d thus constructed, inverse converting processes corresponding to the respective converting processes in the image coding apparatus 200c shown in FIG. 29 are carried out to a coded image signal, in the reverse order of the order in coding, thereby accurately decoding the coded image signal.
FIG. 33 is a block diagram illustrating a construction of still another conventional image coding apparatus. In FIG. 33, reference numeral 200e designates an image processing apparatus (image coding apparatus), which performs inter-frame predictive coding processing comprising generating predicted values of an image signal (pixel values) of a coding target frame from another frame, and coding difference values between the image signal (pixel values) of the coding target frame and the predicted values.
This image coding apparatus 200e has an information source coding unit 200e2 for performing information source coding to difference values 1002 between an image signal (pixel values) 103 obtained by blocking and predicted values 1008 of the image signal 103, in place of the information source coding unit 200a1 in the image coding apparatus 200a shown in FIG. 26, which performs information source coding to the image signal 103. Further, the image coding apparatus 200e has a scanning unit 200e1 for changing a scan method, i.e., the processing order for coding, according to a parameter 1015 concerning generation of the predicted values 1008, in place of the scanner 109 in the image coding apparatus 200a. 
The information source coding unit 200e2 consists of an adder 1001, a DCT unit 104e, a quantization unit 106e, an inverse quantization unit 203e, an inverse DCT unit 204e, an adder 1010, a frame memory 1014, and a predictor 1012.
The adder 1001 is for subtracting predicted values 1008 from an image signal (pixel values) 103 corresponding to a coding target block. The DCT unit 104e is for transforming difference values 1002 between the image signal (pixel values) 103 and the predicted values 1008 into frequency components (DCT coefficients) 1003 by DCT. The quantization unit 106e is for quantizing the DCT coefficients 1003 to generate quantized values 1004 corresponding to the coding target block.
Further, the inverse quantization unit 203e is for inverse-quantizing the quantized values 1004 output from the quantization unit 106e to output DCT coefficients 1007 corresponding to the DCT coefficients 1003. The inverse DCT unit 204e is for performing inverse DCT to the DCT coefficients 1007 to output difference signals 1009 corresponding to the difference values 1002. The adder 1010 is for adding the predicted values 1008 to the difference signals 1009 to output an already coded image signal 1011 corresponding to the coding target block.
Furthermore, the frame memory 1014 is for temporarily storing already coded image signals 1011 corresponding to one frame or corresponding to frames of a prescribed number. The predictor 1012 is for generating the predicted values 1008 on the basis of an already coded image signal 1013 corresponding to a reference block in the memory 1014 and the image signal 103 corresponding to the coding target block.
The scanning unit 200e1 consists of two scanners 129s1 and 129s2 having different scan methods, for scanning the output of the information source coding unit 200e2, a first switch 108e for selecting one of the two scanners on the basis of a control signal 116e and supplying the output 1004 of the information source coding unit 200e2 to the selected scanner, a second switch 110e for selecting one of the two scanners on the basis of the control signal 116e and supplying an output of the selected scanner to the VLC unit 112, and a scan control unit 1016e for generating the control signal 116e on the basis of a parameter 1015 from the predictor 1012.
Herein, the scanner 129s1 performs a scan of quantized values in the order shown in FIG. 31(a). The scanner 129s2 is constituted by the respective elements 301, 304 and 305 in the prediction unit 200c2 shown in FIG. 29, and the respective elements 108c, 110c, 109s1xcx9c109s3 and 1401c in the scanning unit 200c1 shown in FIG. 29. That is, the scanner 129s2 performs intra-frame prediction to a block to which no inter-frame prediction has been performed in coding (hereinafter referred to as an intra-coded block) and selects one of the scanners 109s1xcx9c109s3 constituting the scanner 129s2 on the basis of prediction information concerning generation of predicted values. In addition, one of the scanners 109s1xcx9c109s3 constituting the scanner 129s2 performs a scan of quantized values in the order shown in FIG. 31(a). The coding processing by the image coding apparatus 200e is fundamentally identical to that by the image coding apparatus 200c shown in FIG. 29, except that difference values between an image signal which is obtained by blocking and predicted values of the image signal are coded.
That is, in inter-frame predictive coding by the image coding apparatus 200e, predicted values 1008 are set to 0 when prediction efficiency is low, whereby an image signal 103 corresponding to a coding target block is subjected to DCT processing as it is (intra-coding). Switching between inter-coding and intra-coding is performed for each macroblock, and information indicating either inter-coding or intra-coding is added to a parameter 1015 concerning prediction.
Further, when a coding target block is an inter-coded macroblock, the scanner 129s1 is selected. When the coding target block is an intra-coded macroblock, the scanner 129s2 is selected. Thereby, a scan method suitable for each coding is executed.
Specifically, quantized values corresponding to an intra-coded macroblock are supplied to the scanner 129s2 comprising the prediction unit 200c2 and the scanning unit 200c1 shown in FIG. 29. In the scanner 129s2, predicted values of the quantized values are generated by intra-frame prediction, and an adaptive scan is performed to difference values between the quantized values of the coding target block and the predicted values, on the basis of prediction information concerning generation of the predicted values.
Meanwhile, quantized values corresponding to an inter-coded macroblock are supplied to the scanner 129s1, and a scan in the order shown in FIG. 31(a) is performed in the scanner 129s1.
In the image coding apparatus 200e thus constructed, since the difference values are coded, many DCT coefficients become 0 by quantization, whereby the efficiency of variable-length coding is improved.
In addition, in the image coding apparatus 200e, no intra-frame prediction may be carried out to an intra-coded macroblock. In this case, one of the scanners l09s1xcx9c109s3 constituting the scanner 129s2 performs a scan in the order shown in FIG. 31(a) to quantized values of the intra-coded macroblock.
FIG. 34 is a block diagram illustrating a construction of an image decoding apparatus corresponding to the image coding apparatus 200e shown in FIG. 33. In FIG. 34, reference numeral 200f designates an image processing apparatus (image decoding apparatus), which decodes the coded image signal 1006 that has been coded in the image coding apparatus 200e. 
This image decoding apparatus 200f has an inverse scanning unit 200f1 for performing an inverse scan to quantized values 1005 which are obtained by variable-length decoding of the coded image signal 1006 so that the order of the quantized values is returned to the order before scanning in coding, and changing an inverse scan method on the basis of the parameter 1015 concerning generation of predicted values in the image coding apparatus 200e, in place of the inverse scanner 202 in the image decoding apparatus 200b shown in FIG. 28. Further, the image decoding apparatus 200f has an information source decoding unit 200f2 for performing information source decoding to quantized values 1004 corresponding to a decoding target block which have been subjected to inverse scanning, in place of the information source de-coding unit 200b1 in the image decoding apparatus 200b. 
The inverse scanning unit 200f1 consists of two inverse scanners 222s1 and 222s2 having different inverse scan methods, for inverse-scanning the output 1005 of the VLD unit 201, a first switch 108f for selecting one of the two inverse scanners on the basis of a control signal 116f and supplying the output 1005 of the VLD unit 201 to the selected inverse scanner, a second switch 110f for selecting one of the two inverse scanners on the basis of the control signal 116f and supplying the output of the selected inverse scanner to the information source decoding unit 200f2, and an inverse scan control unit 1016f for generating the control signal 116f on the basis of the prediction parameter 1015. Herein, the inverse scanners 222s1 and 222s2 correspond to the scanners 129s1 and 129s2 in the image coding apparatus 200e. 
That is, the inverse scanner 222s1 performs an inverse scan corresponding to a scan in the order shown in FIG. 31(a), and the inverse scanner 222s2 is constituted by the respective elements 108d, 110d, 202s1xcx9c202s3 and 1401d in the inverse scanning unit 200d1 shown in FIG. 32, and the respective elements 304 and 401 in the prediction unit 200d2 shown in FIG. 32.
The information source decoding unit 200f2 consists of an inverse quantization unit 203f for inverse-quantizing the output 1004 of the inverse scanning unit 200f1, an inverse DCT unit 204f for performing inverse DCT processing to an output 1003 of the inverse quantization unit 203f, an adder 1101f for adding predicted values 1008f of the decoding target block to an output 1002 of the inverse DCT unit 204f. 
Further, the information source decoding unit 200f2 consists of a frame memory 1014f for temporarily storing already decoded image signals 103 corresponding to one frame or frames of a prescribed number, and a predictor 1102f for generating the predicted values 1008f of the decoding target block on the basis of an already decoded image signal 1013f corresponding to a reference block in the memory 1014f and the parameter 1015 concerning prediction in coding.
In the image decoding apparatus 200f thus constructed, inverse converting processes corresponding to the respective converting processes in the image coding apparatus 200e shown in FIG. 33 are carried out to a coded image signal, in the reverse order of the order in coding, thereby accurately decoding the coded image signal.
The scan changing method in any of the conventional image processing apparatuses is available for progressive image coding in which all blocks are frame DCT blocks. However, in interlaced image coding in which frame DCT blocks and field DCT blocks coexist, since a field DCT block and a frame DCT block have different distributions of DCT coefficients, coefficients of about the same size are not consecutive when the same scan changing method is used, so that the efficiency of variable-length coding is degraded.
That is, in interlaced image coding in which either frame DCT processing or field DCT processing is adaptively selected for each macroblock and macroblocks having different DCT types coexist, when a scan method is changed using a parameter concerning generation of predicted values, since a field DCT block and a frame DCT block have different distributions of DCT coefficients, coefficients of about the same size are not consecutive, so that the efficiency of variable-length coding is degraded.
Further, also in inter-frame predictive coding of an interlaced image in any of the conventional image processing apparatuses, the above-mentioned problem arises because macroblocks having different DCT types coexist.
Furthermore, also in coding of a progressive image, when switching is performed between frame DCT processing and field DCT processing according to the content of the image, for example, in a case where frame DCT processing is executed when correlations between adjacent scan lines are strong and field DCT processing is executed when correlations between adjacent scan lines are weak, the efficiency of variable-length coding is degraded as in the interlaced image coding.
It is an object of the present invention to provide image processing apparatuses and image processing methods in which, in coding of an interlaced image in which macroblocks having different DCT types coexist, or in coding of a specific progressive image, a scan method that improves the efficiency of variable-length coding can be adaptively selected, thereby realizing highly efficient coding.
Another object of the present invention is to provide data recording media in which image processing programs for implementing the above-mentioned image processing methods are recorded.
Other objects and advantages of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific embodiment are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description.
According to a first aspect of the present invention, an image processing method for dividing a digital image signal into plural image signals corresponding to plural blocks constituting a single display screen, and performing block-by-block coding of the image signals of the respective blocks, comprises transforming an image signal of a coding target block to be subjected to coding into frequency components by one of frame-by-frame frequency transformation on a frame basis and field-by-field frequency transformation on a field basis; setting a processing order for coding the frequency components corresponding to the image signal of the coding target block, according as the image signal of the coding target block has been subjected to the frame-by-frame frequency transformation or the field-by-field frequency transformation; and successively coding the frequency components corresponding to the image signal of the coding target block according to the order which has been set.
Thus, a processing order for coding is set to frequency components corresponding to an image signal of a coding target block, according as the image signal of the coding target block has been subjected to frame-by-frame frequency transformation or field-by-field frequency transformation. Therefore, in coding of an interlaced image in which frame DCT blocks and field DCT blocks coexist, a run length is increased, thereby improving coding efficiency in the interlaced image coding. In addition, in coding of a specific progressive image in which frame DCT blocks and field DCT blocks coexist, the same effect is obtained.
According to a second aspect of the present invention, an image processing method for performing block-by-block decoding of a coded image signal that is obtained by performing a coding process including frequency transformation to a digital image signal, for each of blocks constituting a single display screen, comprises performing rearrangement to an input signal that is obtained by coding various frequency components in a prescribed order, in an order which is decided according as an image signal corresponding to a decoding target block to be subjected to decoding has been subjected to frame-by-frame frequency transformation on a frame basis or field-by-field frequency transformation on a field basis, thereby generating frequency components corresponding to the decoding target block; and performing inverse frequency transformation to the frequency components corresponding to the decoding target block to regenerate an image signal corresponding to the decoding target block.
Thus, an input signal that is obtained by coding various frequency components in a prescribed order is subjected to rearrangement in an order which is decided according as an image signal corresponding to a decoding target block to be subjected to decoding has been subjected to frame-by-frame frequency transformation on a frame basis or field-by-field frequency transformation on a field basis, thereby generating frequency components corresponding to the decoding target block. Therefore, in variable-length decoding of DCT coefficients of either a progressive image or an interlaced image, accurate and efficient decoding can be carried out to a bit stream which has been coded using an adaptive scan changing method, i.e., a method for adaptively changing a processing order for coding, thereby regenerating an image signal.
According to a third aspect of the present invention, an image processing method for dividing a digital image signal into plural image signals corresponding to plural blocks constituting a single display screen, and performing block-by-block coding of the image signals of the respective blocks, comprises transforming an image signal of a coding target block to be subjected to coding into frequency components by one of frame-by-frame frequency transformation on a frame basis and field-by-field frequency transformation on a field basis; setting a processing order for coding the frequency components corresponding to the image signal of the coding target block, according to a combination pattern of the kind of frequency transformation to which the image signal of the coding target block has been subjected and the kind of frequency transformation to which an image signal of an already coded block located in the vicinity of the coding target block has been subjected; and successively coding the frequency components corresponding to the image signal of the coding target block according to the order which has been set.
Thus, a processing order for coding is set to frequency components corresponding to an image signal of a coding target block, according to a combination pattern of the kind of frequency transformation to which the image signal of the coding target block has been subjected and the kind of frequency transformation to which an image signal of an already coded block located in the vicinity of the coding target block has been subjected. Therefore, scanning processing for setting a coding order is controlled more finely and a more suitable scan is selected. Consequently, a run length is more increased, resulting in further improved coding efficiency.
According to a fourth aspect of the present invention, an image processing method for performing block-by-block decoding of a coded image signal that is obtained by performing a coding process including frequency transformation to a digital image signal, for each of blocks constituting a single display screen, comprises performing rearrangement to an input signal that is obtained by coding various frequency components in a prescribed order, in an order which is decided according to a combination pattern of frequency transformation to which an image signal corresponding to a decoding target block to be subjected to decoding has been subjected and frequency transformation to which an image signal corresponding to an already decoded block located in the vicinity of the decoding target block has been subjected, thereby generating frequency components corresponding to the decoding target block; and performing inverse frequency transformation to the frequency components corresponding to the decoding target block to regenerate an image signal corresponding to the decoding target block.
Thus, an input signal that is obtained by coding various frequency components in a prescribed order is subjected to rearrangement in an order which is decided according to a combination pattern of frequency transformation to which an image signal corresponding to a decoding target block to be subjected to decoding has been subjected and frequency transformation to which an image signal corresponding to an already decoded block located in the vicinity of the decoding target block has been subjected, thereby generating frequency components corresponding to the decoding target block. Therefore, in variable-length decoding of DCT coefficients of either a progressive image or an interlaced image, accurate and efficient decoding can be carried out to a bit stream which has been coded using an adaptive scan changing method, i.e., a method for adaptively changing a processing order for coding, thereby regenerating an image signal.
According to a fifth aspect of the present invention, an image processing method for dividing a digital image signal into plural image signals corresponding to plural blocks constituting a single display screen, and performing block-by-block coding of the image signals of the respective blocks, comprises transforming an image signal of a coding target block to be subjected to coding into frequency components by one of frame-by-frame frequency transformation on a frame basis and field-by-field frequency transformation on a field basis; generating predicted values of the frequency components corresponding to the coding target block from frequency components corresponding to an already coded block located in the vicinity of the coding target block, by a prescribed prediction process; setting a processing order for coding difference values between the frequency components of the coding target block and the predicted values, according to a combination pattern of the kind of frequency transformation to which the image signal of the coding target block has been subjected and the kind of the prediction process; and successively coding the difference values corresponding to the coding target block according to the order which has been set.
Thus, a processing order for coding is set to difference values between frequency components of a coding target block and predicted values of the frequency components, according to a combination pattern of the kind of frequency transformation to which an image signal of the coding target block has been subjected and the kind of a prediction process. Therefore, in coding of an interlaced image in which frame DCT blocks and field DCT blocks coexist, a run length is increased, thereby improving coding efficiency.
According to a sixth aspect of the present invention, an image processing method for performing block-by-block decoding of a coded image signal that is obtained by performing a coding process including frequency transformation to a digital image signal, for each of blocks constituting a single display screen, comprises performing rearrangement to an input signal that is obtained by coding various frequency components which have been subjected to a prediction process in a prescribed order, in an order which is decided according to a combination pattern of the kind of frequency transformation to which an image signal corresponding to a decoding target block to be subjected to decoding has been subjected and the kind of the prediction process; generating predicted values of frequency components corresponding to the decoding target block from frequency components corresponding to an already decoded block located in the vicinity of the decoding target block, on the basis of the kind of the prediction process; generating frequency components corresponding to the decoding target block on the basis of the input signal after the rearrangement and the predicted values; and performing inverse frequency transformation to the frequency components corresponding to the decoding target block to regenerate an image signal corresponding to the decoding target block.
Thus, an input signal that is obtained by coding various frequency components which have been subjected to a prediction process in a prescribed order is subjected to rearrangement in an order which is decided according to a combination pattern of the kind of frequency transformation to which an image signal corresponding to a decoding target block to be subjected to decoding has been subjected and the kind of the prediction process; and predicted values of frequency components corresponding to the decoding target block are generated from frequency components corresponding to an already decoded block located in the vicinity of the decoding target block, on the basis of the kind of the prediction process. Therefore, in variable-length decoding of DCT coefficients of either a progressive image or an interlaced image, accurate and efficient decoding can be carried out to a bit stream which has been coded using a fine and adaptive scan changing method, i.e., a method for finely and adaptively changing a processing order for coding, thereby regenerating an image signal.
According to a seventh aspect of the present invention, an image processing method for dividing a digital image signal into plural image signals corresponding to plural blocks constituting a single display screen, and performing block-by-block coding of the image signals of the respective blocks, comprises transforming an image signal of a coding target block to be subjected to coding into frequency components by one of frame-by-frame frequency transformation on a frame basis and field-by-field frequency transformation on a field basis; generating predicted values of the frequency components corresponding to the coding target block from frequency components corresponding to an already coded block located in the vicinity of the coding target block, by a prescribed prediction process; setting a processing order for coding difference values between the frequency components of the coding target block and the predicted values, according to a combination pattern of the kind of frequency transformation to which the image signal of the coding target block has been subjected, the kind of frequency transformation to which an image signal of the already coded block located in the vicinity of the coding target block has been subjected, and the kind of the prediction process; and successively coding the difference values corresponding to the coding target block according to the order which has been set.
Thus, a processing order for coding is set to difference values between frequency components of a coding target block and predicted values of the frequency components, according to a combination pattern of the kind of frequency transformation to which an image signal of the coding target block has been subjected, the kind of frequency transformation to which an image signal of an already coded block located in the vicinity of the coding target block has been subjected, and the kind of a prediction process. Therefore, scanning processing for setting a coding order is controlled more finely and a more suitable scan is selected. Consequently, a run length is more increased, resulting in further improved coding efficiency.
According to an eighth aspect of the present invention, an image processing method for performing block-by-block decoding of a coded image signal that is obtained by performing a coding process including frequency transformation to a digital image signal, for each of blocks constituting a single display screen, comprises performing rearrangement to an input signal that is obtained by coding various frequency components which have been subjected to a prediction process in a prescribed order, in an order which is decided according to a combination pattern of the kind of frequency transformation to which an image signal corresponding to a decoding target block to be subjected to decoding has been subjected, the kind of frequency transformation to which an image signal corresponding to an already decoded target block located in the vicinity of the decoding target block has been subjected, and the kind of the prediction process; generating predicted values of frequency components corresponding to the decoding target block from frequency components corresponding to the already decoded block located in the vicinity of the decoding target block, on the basis of the kind of the prediction process; generating frequency components corresponding to the decoding target block on the basis of the input signal after the rearrangement and the predicted values; and performing inverse frequency transformation to the frequency components corresponding to the decoding target block to regenerate an image signal corresponding to the decoding target block.
Thus, an input signal that is obtained by coding various frequency components which have been subjected to a prediction process in a prescribed order is subjected to rearrangement in an order which is decided according to a combination pattern of the kind of frequency transformation to which an image signal corresponding to a decoding target block to be subjected to decoding has been subjected, the kind of frequency transformation to which an image signal corresponding to an already decoded block located in the vicinity of the decoding target block has been subjected, and the kind of the prediction process, and predicted values of frequency components corresponding to the decoding target block are generated from frequency components corresponding to the already decoded block located in the vicinity of the decoding target block, on the basis of the kind of the prediction process. Therefore, accurate and efficient decoding can be carried out to a bit stream which has been coded using a fine and adaptive scan changing method, i.e., a method for finely and adaptively changing a processing order for coding, thereby regenerating an image signal.
According to a ninth aspect of the present invention, an image processing apparatus for dividing an input digital image signal into plural image signals corresponding to plural blocks constituting a single display screen, and performing block-by-block coding of the image signals of the respective blocks, comprises a blocking unit for blocking the digital image signal correspondingly to the respective blocks, frame by frame or field by field, which is used as a processing unit of frequency transformation, and outputting the blocked image signal and frequency transformation type information indicating the processing unit of frequency transformation; a frequency transformation unit for performing block-by-block frequency transformation to the blocked image signal to output frequency components corresponding to the image signal of each block; a quantization unit for quantizing the frequency components to output quantized values corresponding to the image signal of each block; plural scanners having different orders of rearrangement, and each setting a prescribed processing order to the quantized values by rearranging the quantized values; a scan control unit for outputting a control signal for selecting a scanner to be used for rearranging the quantized values, according to the frequency transformation type information; and a variable-length coding unit for performing variable-length coding to the quantized values after the rearrangement.
Thus, a processing order for coding is set to frequency components corresponding to an image signal of a coding target block, according as the image signal of the coding target block has been subjected to frame-by-frame frequency transformation or field-by-field frequency transformation. Therefore, in coding of an interlaced image in which frame DCT blocks and field DCT blocks coexist, a run length is increased, thereby improving coding efficiency in the interlaced image coding. In addition, in coding of a specific progressive image in which frame DCT blocks and field DCT blocks coexist, the same effect is obtained.
According to a tenth aspect of the present invention, an image processing apparatus for performing block-by-block decoding of a coded image signal that is obtained by performing a coding process including frequency transformation on a frame basis or on a field basis to a digital image signal, for each of blocks constituting a single display screen, comprises a variable-length decoding unit for performing variable-length decoding to a coded string that is obtained by performing rearrangement and variable-length coding to quantized values of frequency components of an image signal corresponding to each block; plural inverse scanners having different orders of rearrangement, and each rearranging quantized values which have been rearranged in coding so that the order of the quantized values is returned to the order before the rearrangement, thereby outputting the quantized values; an inverse scan control unit for outputting a control signal for selecting an inverse scanner to be used for rearranging the quantized values, according to frequency transformation type information indicating whether frequency transformation in coding is performed on a frame basis or on a field basis; an inverse quantization unit for inverse-quantizing the quantized values to output frequency components of an image signal corresponding to each block; an inverse frequency transformation unit for performing inverse frequency transformation to the frequency components to output an image signal corresponding to each block; and an inverse blocking unit for inverse-blocking the image signals of the respective blocks according to the frequency transformation type information to output a digital image signal.
Thus, an input signal that is obtained by coding various frequency components in a prescribed order is subjected to rearrangement in an order which is decided according as an image signal corresponding to a decoding target block to be subjected to decoding has been subjected to frame-by-frame frequency transformation on a frame basis or field-by-field frequency transformation on a field basis, thereby generating frequency components corresponding to the decoding target block. Therefore, in variable-length decoding of DCT coefficients of either a progressive image or an interlaced image, accurate and efficient decoding can be carried out to a bit stream which has been coded using an adaptive scan changing method, i.e., a method for adaptively changing a processing order for coding, thereby regenerating an image signal.
According to an eleventh aspect of the present invention, an image processing apparatus for dividing an input digital image signal into plural image signals corresponding to plural blocks constituting a single display screen, and performing block-by-block coding of the image signals of the respective blocks, comprises a blocking unit for blocking the digital image signal correspondingly to the respective blocks, frame by frame or field by field, which is used as a processing unit of frequency transformation, and outputting the blocked image signal and frequency transformation type information indicating the processing unit of frequency transformation; a frequency transformation unit for performing block-by-block frequency transformation to the blocked image signal to output frequency components corresponding to the image signal of each block; a quantization unit for quantizing the frequency components to output quantized values corresponding to the image signal of each block; a predictor for generating predicted values of quantized values corresponding to a coding target block to be subjected to coding, from quantized values corresponding to an already coded block located in the vicinity of the coding target block, and outputting the predicted values and prediction information concerning the kind of the generating process of the predicted values; a first adder for subtracting the predicted values from the quantized values corresponding to the coding target block to output difference values; a second adder for adding the predicted values to the difference values to output the result of the addition as quantized values corresponding to an already coded block; plural scanners having different orders of rearrangement, and each rearranging the difference values; a scan control unit for outputting a control signal for selecting a scanner to be used for rearranging the difference values, according to the prediction information and the frequency transformation type information; and a variable-length coding unit for performing variable-length coding to the difference values after the rearrangement.
Thus, a processing order for coding is set to difference values between frequency components of a coding target block and predicted values of the frequency components, according to a combination pattern of the kind of frequency transformation to which an image signal of the coding target block has been subjected and the kind of a prediction process. Therefore, in coding of an interlaced image in which frame DCT blocks and field DCT blocks coexist, a run length is increased, thereby improving coding efficiency.
According to a twelfth aspect of the present invention, an image processing apparatus for performing block-by-block decoding of a coded image signal that is obtained by performing a coding process including frequency transformation to a digital image signal, for each of blocks constituting a single display screen, comprises a variable-length decoding unit for performing variable-length decoding to a coded string that is obtained by performing prediction, rearrangement, and variable-length coding to quantized values of frequency components of an image signal corresponding to each block; plural inverse scanners having different orders of rearrangement, and each rearranging quantized values which have been rearranged in coding so that the order of the quantized values is returned to the order before the rearrangement; an inverse scan control unit for outputting a control signal for selecting an inverse scanner to be used for rearranging the quantized values, according to frequency transformation type information indicating the kind of frequency transformation in coding and prediction information indicating the kind of prediction in coding; an inverse quantization unit for inverse-quantizing the quantized values to output frequency components of an image signal corresponding to each block; an inverse frequency transformation unit for performing inverse frequency transformation to the frequency components to output an image signal corresponding to each block; and an inverse blocking unit for inverse-blocking the image signals of the respective blocks according to the frequency transformation type information to output a digital image signal.
Thus, an input signal that is obtained by coding various frequency components which have been subjected to a prediction process in a prescribed order is subjected to rearrangement in an order which is decided according to a combination pattern of the kind of frequency transformation to which an image signal corresponding to a decoding target block to be subjected to decoding has been subjected and the kind of the prediction process, and predicted values of frequency components corresponding to the decoding target block are generated from frequency components corresponding to an already decoded block located in the vicinity of the decoding target block, on the basis of the kind of the prediction process. Therefore, in variable-length decoding of DCT coefficients of either a progressive image or an interlaced image, accurate and efficient decoding can be carried out to a bit stream which has been coded using a fine and adaptive scan changing method, i.e., a method for finely and adaptively changing a processing order for coding, thereby regenerating an image signal.
According to a thirteenth aspect of the present invention, an image processing method for dividing a digital image signal into plural image signals corresponding to plural blocks constituting a single display screen, and performing block-by-block coding of the image signals of the respective blocks, comprises transforming an image signal of a coding target block to be subjected to coding into frequency components by one of frame-by-frame frequency transformation on a frame basis and field-by-field frequency transformation on a field basis; setting a processing order for coding the frequency components corresponding to the image signal of the coding target block, according to a distribution of frequency components corresponding to an image signal of an already coded block; and successively coding the frequency components corresponding to the image signal of the coding target block according to the order which has been set.
Thus, a processing order for coding is set to frequency components corresponding to a coding target block, according to a processing order for coding suitable for frequency components corresponding to an already coded block. Therefore, in coding of an interlaced image in which frame DCT blocks and field DCT blocks coexist, a run length is increased, thereby improving coding efficiency. In addition, in coding of a specific progressive image in which frame DCT blocks and field DCT blocks coexist, the same effect is obtained.
According to a fourteenth aspect of the present invention, an image processing method for performing block-by-block decoding of a coded image signal that is obtained by performing a coding process including frequency transformation to a digital image signal, for each of blocks constituting a single display screen, comprises performing rearrangement to an input signal that is obtained by coding various frequency components in a prescribed order, in an order which is decided according to a distribution of frequency components of an image signal corresponding to an already decoded block, thereby generating frequency components corresponding to a decoding target block to be subjected to decoding; and performing inverse frequency transformation to the frequency components corresponding to the decoding target block to regenerate an image signal corresponding to the decoding target block.
Thus, an input signal that is obtained by coding various frequency components in a prescribed order is subjected to rearrangement in an order which is decided according to a processing order for coding suitable for frequency components corresponding to an already decoded block, thereby generating frequency components corresponding to a decoding target block to be subjected to decoding. Therefore, in variable-length decoding of DCT coefficients of either a progressive image or an interlaced image, accurate and efficient decoding can be carried out to a bit stream which has been coded using a fine and adaptive scan changing method, i.e., a method for finely and adaptively changing a processing order for coding, thereby regenerating an image signal.
According to a fifteenth aspect of the present invention, an image processing method for dividing a digital image signal into plural image signals corresponding to plural blocks constituting a single display screen, and performing block-by-block coding of the image signals of the respective blocks, comprises transforming an image signal of a coding target block to be subjected to coding into frequency components by one of frame-by-frame frequency transformation on a frame basis and field-by-field frequency transformation on a field basis; generating predicted values of the frequency components corresponding to the coding target block from frequency components corresponding to an already coded block located in the vicinity of the coding target block, by a prescribed prediction process; setting a processing order for coding difference values between the frequency components of the coding target block and the predicted values, with switching, on the basis of flag information indicating whether adaptive order setting is carried out or not, between the first order setting operation in which a processing order is adaptively set according to the kind of the prediction process, and the second order setting operation in which a specific processing order is set regardless of the kind of the prediction process; and successively coding the difference values corresponding to the coding target block according to the processing order which has been set, and transmitting/storing a resulting coded signal, together with the flag information.
Thus, in coding, an adaptive scan is switched to OFF to execute a specific scan suitable for an interlaced image or a specific progressive image when required, whereby coding of an interlaced image or a specific progressive image can be efficiently simplified.
According to a sixteenth aspect of the present invention, an image processing method for performing block-by-block decoding of a coded image signal that is obtained by performing a coding process including frequency transformation to a digital image signal, for each of blocks constituting a single display screen, comprises performing rearrangement to an input signal that is obtained by coding various frequency components which have been subjected to a prediction process in a prescribed order, with switching, on the basis of flag information indicating whether adaptive rearrangement is carried out or not, which information is input together with the input signal, between the first rearrangement operation in which the input signal is subjected to adaptive rearrangement in an order according to the kind of the prediction process, and the second rearrangement operation in which the input signal is subjected to rearrangement in a specific order, regardless of the kind of the prediction process; generating predicted values of frequency components corresponding to a decoding target block to be subjected to decoding from frequency components corresponding to an already decoded block located in the vicinity of the decoding target block, on the basis of the kind of the prediction process; generating frequency components corresponding to the decoding target block on the basis of the input signal after the rearrangement and the predicted values; and performing inverse frequency transformation to the frequency components corresponding to the decoding target block to regenerate an image signal corresponding to the decoding target block.
Thus, in decoding, an adaptive inverse scan is switched to OFF to execute a specific inverse scan suitable for an interlaced image or a specific progressive image when required, whereby accurate decoding can be carried out to an interlaced image or a specific progressive image which has been subjected to a specific scan by switching an adaptive scan to OFF in coding.
According to a seventeenth aspect of the present invention, an image processing method for dividing a digital image signal into plural image signals corresponding to plural blocks constituting a single display screen, and performing block-by-block coding of the image signals of the respective blocks, comprises generating predicted values of an image signal of a coding target block to be subjected to coding from an image signal corresponding to an already coded display screen different from a display screen including the coding target block, by a prescribed prediction process; transforming difference values between the image signal of the coding target block and the predicted values into frequency components by one of frame-by-frame frequency transformation on a frame basis and field-by-field frequency transformation on a field basis; setting a processing order for coding the frequency components of the coding target block, with switching, on the basis of flag information indicating whether adaptive order setting is carried out or not, between the first order setting operation in which a processing order is adaptively set according to the kind of the prediction process, and the second order setting operation in which a specific processing order is set regardless of the kind of the prediction process; and successively coding the frequency components corresponding to the coding target block according to the processing order which has been set, and transmitting/storing a resulting coded signal, together with the flag information.
Thus, in coding, since, for each of intra-coded macroblocks and inter-coded macroblocks, one of plural scans is selected according to a parameter concerning prediction and a scan switching signal, a scan suitable for each coding method is performed. Therefore, in inter coding of an interlaced image in which inter-coded macroblocks and intra-coded macroblocks having different frequency component distributions coexist, a run length is increased, thereby improving coding efficiency. In addition, in inter coding of a specific progressive image in which inter-coded macroblocks and intra-coded macroblocks having different frequency component distributions coexist, the same effect is obtained.
According to an eighteenth aspect of the present invention, an image processing method for performing block-by-block decoding of a coded image signal that is obtained by performing a coding process including frequency transformation to a digital image signal, for each of blocks constituting a single display screen, comprises performing rearrangement to an input signal that is obtained by coding various frequency components which have been subjected to a prediction process in a prescribed order, with switching, on the basis of flag information indicating whether adaptive rearrangement is carried out or not, which information is input together with the input signal, between the first rearrangement operation in which the input signal is subjected to adaptive rearrangement in an order according to the kind of the prediction process, and the second rearrangement operation in which the input signal is subjected to rearrangement in a specific order, regardless of the kind of the prediction process; performing inverse frequency transformation to the input signal after the rearrangement to generate a difference signal corresponding to a decoding target block to be subjected to decoding; generating predicted values of an image signal of the decoding target block from an image signal corresponding to an already decoded display screen different from a display screen including the decoding target block, on the basis of the kind of the prediction process; and regenerating an image signal corresponding to the decoding target block on the basis of the difference signal and the predicted values.
Thus, in decoding, for each of intra-coded macroblocks and inter-coded macroblocks, one of plural inverse scans is selected according to a parameter concerning prediction and a scan switching signal. Therefore, accurate and efficient decoding can be carried out to a bit stream which has been coded by selecting one of plural scans for each of intra-coded macroblocks and inter-coded macroblocks, according to the parameter concerning prediction and the scan switching signal, thereby regenerating an image signal.
According to a nineteenth aspect of the present invention, an image processing apparatus for dividing an input digital image signal into plural image signals corresponding to plural blocks constituting a single display screen, and performing block-by-block coding of the image signals of the respective blocks, comprises a blocking unit for blocking the digital image signal correspondingly to the respective blocks, frame by frame or field by field, which is used as a processing unit of frequency transformation, and outputting the blocked image signal and frequency transformation type information indicating the processing unit of frequency transformation; a frequency transformation unit for performing block-by-block frequency transformation to the blocked image signal to output frequency components corresponding to the image signal of each block; a quantization unit for quantizing the frequency components to output quantized values corresponding to the image signal of each block; plural scanners having different orders of rearrangement, and each setting a prescribed processing order to the quantized values by rearranging the quantized values; a characteristic analyzing unit for performing characteristic analysis of the output of the quantization unit to output a scan specifying signal for specifying a scanner which performs rearrangement suitable for the quantized values of each block; a memory for temporarily storing the scan specifying signals from the characteristic analyzing unit; a scan control unit for outputting a control signal for selecting a scanner to be used for rearranging quantized values of a coding target block to be subjected to coding, according to the scan specification signals which are stored in the memory; and a variable-length coding unit for performing variable-length coding to the quantized values after the rearrangement.
Thus, a processing order for coding is set to frequency components corresponding to a coding target block, according to a processing order for coding suitable for frequency components corresponding to an already coded block. Therefore, in coding of an interlaced image in which frame DCT blocks and field DCT blocks coexist, a run length is increased, thereby improving coding efficiency. In addition, in coding of a specific progressive image in which frame DCT blocks and field DCT blocks coexist, the same effect is obtained.
According to a twentieth aspect of the present invention, an image processing apparatus for performing block-by-block decoding of a coded image signal that is obtained by performing a coding process including frequency transformation on a frame basis or on a field basis to a digital image signal, for each of blocks constituting a single display screen, comprises a variable-length decoding unit for performing variable-length decoding to a coded string that is obtained by performing rearrangement and variable-length coding to quantized values of frequency components of an image signal corresponding to each block; plural inverse scanners having different orders of rearrangement, and each rearranging quantized values which have been rearranged in coding so that the order of the quantized values is returned to the order before the rearrangement; a characteristic analyzing unit for performing characteristic analysis of the output of the inverse scanner to output a scan specifying signal for specifying an inverse scanner which performs rearrangement suitable for the quantized values of each block; a memory for temporarily storing the scan specifying signals from the characteristic analyzing unit; an inverse scan control unit for outputting a control signal for selecting an inverse scanner to be used for rearranging quantized values of a decoding target block to be subjected to decoding, according to the scan specification signals which are stored in the memory; an inverse quantization unit for inverse-quantizing the quantized values output from the selected inverse scanner to output frequency components of an image signal corresponding to each block; an inverse frequency transformation unit for performing inverse frequency transformation to the frequency components to output an image signal corresponding to each block; and an inverse blocking unit for inverse-blocking the image signals of the respective blocks according to frequency transformation type information indicating whether frequency transformation in coding is performed on a frame basis or on a field basis, to output a digital image signal.
Thus, an input signal that is obtained by coding various frequency components in a prescribed order is subjected to rearrangement in an order which is decided according to a processing order for coding suitable for frequency components corresponding to an already decoded block, thereby generating frequency components corresponding to a decoding target block to be subjected to decoding. Therefore, in variable-length decoding of DCT coefficients of either a progressive image or an interlaced image, accurate and efficient decoding can be carried out to a bit stream which has been coded using a fine and adaptive scan changing method, i.e., a method for finely and adaptively changing a processing order for coding, thereby regenerating an image signal.
According to a twenty-first aspect of the present invention, an image processing apparatus for dividing an input digital image signal into plural image signals corresponding to plural blocks constituting a single display screen, and performing block-by-block coding of the image signals of the respective blocks, comprises a blocking unit for blocking the digital image signal correspondingly to the respective blocks, frame by frame or field by field, which is used as a processing unit of frequency transformation, and outputting the blocked image signal and frequency transformation type information indicating the processing unit of frequency transformation; a frequency transformation unit for performing block-by-block frequency transformation to the blocked image signal to output frequency components corresponding to the image signal of each block; a quantization unit for quantizing the frequency components to output quantized values corresponding to the image signal of each block; a predictor for generating predicted values of quantized values corresponding to a coding target block to be subjected to coding, from quantized values corresponding to an already coded block located in the vicinity of the coding target block, and outputting the predicted values and prediction information concerning the kind of the generating process of the predicted values; a first adder for subtracting the predicted values from the quantized values corresponding to the coding target block to output difference values; a second adder for adding the predicted values to the difference values to output the result of the addition as quantized values corresponding to an already coded block; plural scanners having different orders of rearrangement, and each being selected by a selecting signal and rearranging the difference values; a scan control unit for outputting a first control signal for selecting a scanner to be used for rearranging the difference values, according to the prediction information; a switch for selecting one of the first control signal and a second control signal for selecting a specific scan, according to a scan changing signal which is generated outside/inside a system, and outputting the selected control signal as the selecting signal of the scanner; and a variable-length coding unit for performing variable-length coding to the difference values after the rearrangement.
Thus, in coding, an adaptive scan is switched to OFF to execute a specific scan suitable for an interlaced image or a specific progressive image when required, whereby coding of an interlaced image or a specific progressive image can be efficiently simplified.
According to a twenty-second aspect of the present invention, an image processing apparatus for performing block-by-block decoding of a coded image signal that is obtained by performing a coding process including frequency transformation on a frame basis or on a field basis to a digital image signal, for each of blocks constituting a single display screen, comprises a variable-length decoding unit for performing variable-length decoding to a coded string that is obtained by performing prediction, rearrangement, and variable-length coding to quantized values of frequency components of an image signal corresponding to each block; plural inverse scanners having different orders of rearrangement, and each being selected by a selecting signal, and rearranging quantized values which have been rearranged in coding so that the order of the quantized values is returned to the order before the rearrangement; an inverse scan control unit for outputting a first control signal for selecting an inverse scanner to be used for rearranging the quantized values, according to prediction information indicating the kind of prediction in coding; a switch for selecting one of the first control signal and a second control signal for selecting a specific scan, according to a scan changing signal, and outputting the selected control signal as the selecting signal of the inverse scanner; a predictor for generating predicted values of quantized values corresponding to a decoding target block to be subjected to decoding, from quantized values corresponding to an already decoded block located in the vicinity of the decoding target block, according to the prediction information; an adder for adding the predicted values to the output of the inverse scanner; an inverse quantization unit for inverse-quantizing the output of the adder to output frequency components of an image signal corresponding to each block; an inverse frequency transformation unit for performing inverse frequency transformation to the frequency components to output an image signal corresponding to each block; and an inverse blocking unit for inverse-blocking the image signals of the respective blocks according to frequency transformation type information indicating whether frequency transformation in coding is performed on a frame basis or on a field basis, to output a digital image signal.
Thus, in decoding, an adaptive inverse scan is switched to OFF to execute a specific inverse scan suitable for an interlaced image or a specific progressive image when required, whereby accurate decoding can be carried out to an interlaced image or a specific progressive image which has been subjected to a specific scan by switching an adaptive scan to OFF in coding.
According to a twenty-third aspect of the present invention, an image processing apparatus for dividing an input digital image signal into plural image signals corresponding to plural blocks constituting a single display screen, and performing block-by-block coding of the image signals of the respective blocks, comprises a blocking unit for blocking the digital image signal correspondingly to the respective blocks, frame by frame or field by field, which is used as a processing unit of frequency transformation, and outputting the blocked image signal and frequency transformation type information indicating the processing unit of frequency transformation; a first adder for subtracting predicted values of the blocked image signal from the blocked image signal to output a difference signal; a frequency transformation unit for performing block-by-block frequency transformation to the difference signal to output frequency components corresponding to the difference signal of each block; a quantization unit for quantizing the frequency components to output quantized values corresponding to the image signal of each block; an inverse quantization unit for inverse-quantizing the quantized values to output the frequency components corresponding to the difference signal of each block; an inverse frequency transformation unit for performing inverse frequency transformation to the output of the inverse quantization unit to output the difference signal of each block; a second adder for adding the predicted values to the output of the inverse frequency transformation unit, and storing the result of the addition in a frame memory, as an image signal of an already coded block as a constituent of an already coded display screen; a predictor for generating the predicted values on the basis of the image signal of each block and an image signal of an already coded block which is stored in the frame memory, and outputting the predicted values and prediction information concerning the generating process of the predicted values; plural scanners having different orders of rearrangement, and each rearranging the quantized values; a scan control unit for outputting a control signal for selecting a scanner to be used for rearranging the quantized values, according to a scan changing signal which is generated outside/inside a system and the prediction information; and a variable-length coding unit for performing variable-length coding to the quantized values after the rearrangement.
Thus, in coding, since, for each of intra-coded macroblocks and inter-coded macroblocks, one of plural scans is selected according-to a parameter concerning prediction and a scan switching signal, a scan suitable for each coding method is performed. Therefore, in inter coding of an interlaced image in which inter-coded macroblocks and intra-coded macroblocks having different frequency component distributions coexist, a run length is increased, thereby improving coding efficiency. In addition, in inter coding of a specific progressive image in which inter-coded macroblocks and intra-coded macroblocks having different frequency component distributions coexist, the same effect is obtained.
According to a twenty-fourth aspect of the present invention, an image processing apparatus for performing block-by-block decoding of a coded image signal that is obtained by performing a coding process including frequency transformation on a frame basis or on a field basis to a digital image signal, for each of blocks constituting a single display screen, comprises a variable-length decoding unit for performing variable-length decoding to a coded string that is obtained by performing prediction, frequency transformation, quantization, rearrangement, and variable-length coding to an image signal corresponding to each block; plural inverse scanners having different orders of rearrangement, and each rearranging quantized values which have been rearranged in coding so that the order of the quantized values is returned to the order before the rearrangement; an inverse scan control unit for outputting a control signal for selecting an inverse scanner to be used for rearranging the quantized values, according to a scan changing signal and prediction information indicating the kind of prediction in coding; an inverse quantization unit for inverse-quantizing the output of the inverse scanner to output frequency components of a difference signal corresponding to each block; an inverse frequency transformation unit for performing inverse frequency transformation to the frequency components to output a difference signal corresponding to each block; an adder for adding predicted values of an image signal corresponding to each block to the difference signal to output an image signal corresponding to each block; a frame memory for storing the output of the adder, as an image signal of an already decoded block as a constituent of an already decoded display screen; a predictor for generating the predicted values on the basis of the prediction information and an image signal of an already coded block; and an inverse blocking unit for inverse-blocking the image signals of the respective blocks according to frequency transformation type information indicating whether frequency transformation in coding is performed on a frame basis or on a field basis, to output a digital image signal.
Thus, in decoding, for each of intra-coded macroblocks and inter-coded macroblocks, one of plural inverse scans is selected according to a parameter concerning prediction and a scan switching signal. Therefore, accurate and efficient decoding can be carried out to a bit stream which has been coded by selecting one of plural scans for each of intra-coded macroblocks and inter-coded macroblocks, according to the parameter concerning prediction and the scan switching signal, thereby regenerating an image signal.
According to a twenty-fifth aspect of the present invention, an image processing method for dividing a digital image signal into plural image signals corresponding to plural blocks constituting a single display screen, and performing block-by-block coding of the image signals of the respective blocks, comprises generating inter-frame predicted values of an image signal of a coding target block to be subjected to coding, from an image signal corresponding to an already coded display screen different from a display screen including the coding target block, by a prescribed inter-frame prediction process; transforming one of inter-frame difference values between the image signal of the coding target block and the inter-frame predicted values, and the image signal of the coding target block, into frequency components by one of frame-by-frame frequency transformation on a frame basis and field-by-field frequency transformation on a field basis; generating intra-frame predicted values of the frequency components corresponding to the coding target block from frequency components corresponding to an already coded block located in the vicinity of the coding target block, by a prescribed intra-frame prediction process; setting a processing order for coding intra-frame difference values between the frequency components of the coding target block and the intra-frame predicted values, with switching, on the basis of flag information indicating switching of order setting, between the first order setting operation in which a processing order is adaptively set according to the kinds of both the prediction processes, and the second order setting operation in which a specific processing order is set regardless of the kinds of both the prediction processes; and successively coding the intra-frame difference values corresponding to the coding target block according to the processing order which has been set, and transmitting/storing a resulting coded signal, together with the flag information.
Thus, in coding, switching is performed, on the basis of flag information indicating switching of order setting, between the first order setting operation in which a processing order for coding is adaptively set to intra-frame difference values between frequency components of a coding target block and intra-frame predicted values of the frequency components, according to the kinds of inter-frame prediction and intra-frame prediction processes, and the second order setting operation in which a specific processing order for coding is set thereto, regardless of the kinds of both the prediction processes. Therefore, in inter coding of an interlaced image in which inter-coded macroblocks and intra-coded macroblocks having different frequency component distributions coexist, a run length is still more increased, thereby improving coding efficiency. In addition, in inter coding of a specific progressive image in which inter-coded macroblocks and intra-coded macroblocks having different frequency component distributions coexist, the same effect is obtained.
Specifically, in coding of an interlaced image signal, switching is performed, according to a scan mode switching signal, between a first coding mode in which an adaptive scan is performed to quantized values of an intra-coded block and a zigzag scan is performed to quantized values of an inter-coded block, and a second coding mode in which a scan which gives a priority to a first vertical direction is performed to the quantized values of the intra-coded block and a scan which gives a priority to a second vertical direction is performed to the quantized values of the inter-coded block. Accordingly, in coding of an interlaced image signal in which inter-coded blocks and intra-coded blocks having different frequency component distributions coexist, coding efficiency can be further improved.
According to a twenty-sixth aspect of the present invention, in the image processing method as defined in the twenty-fifth aspect of the invention, an interlaced image signal is received as the digital image signal; in the first order setting operation, concerning an inter-coded block in which the frequency components obtained by the frequency transformation correspond to the inter-frame difference values of the coding target block, the processing order from the side of low-frequency components toward the side of high-frequency components is set so that the components arranged along a horizontal direction of a display screen and the components arranged along a vertical direction have uniform priorities; and concerning an intra-coded block in which the frequency components obtained by the frequency transformation correspond to the image signal of the coding target block, the processing order from the side of low-frequency components toward the side of high-frequency components is adaptively set according to the kind of the intra-frame prediction process; and in the second order setting operation, concerning both the inter-coded block and intra-coded block, the processing order from the side of low-frequency components toward the side of high-frequency components is set so that the components arranged along a vertical direction of a display screen have priority over the components arranged along a horizontal direction.
Thus, in coding, switching is performed, on the basis of flag information indicating switching of order setting, between the first order setting operation in which a processing order for coding is adaptively set to intra-frame difference values between frequency components of a coding target block and intra-frame predicted values of the frequency components, according to the kinds of inter-frame prediction and intra-frame prediction processes, and the second order setting operation in which a specific processing order for coding is set thereto, regardless of the kinds of both the prediction processes. Therefore, in inter coding of an interlaced image in which inter-coded macroblocks and intra-coded macroblocks having different frequency component distributions coexist, a run length is still more increased, thereby improving coding efficiency. In addition, in inter coding of a specific progressive image in which inter-coded macroblocks and intra-coded macroblocks having different frequency component distributions coexist, the same effect is obtained.
According to a twenty-seventh aspect of the present invention, an image processing method for performing block-by-block decoding of a coded image signal that is obtained by performing a coding process including frequency transformation to a digital image signal, for each of blocks constituting a single display screen, comprises performing rearrangement to an input signal of a decoding target block to be subjected to decoding that is obtained by coding various frequency components which have been subjected to an inter-frame prediction process and an intra-frame prediction process in a prescribed order, with switching, on the basis of flag information indicating switching of rearrangement, which information is input together with the input signal, between the first rearrangement operation in which the input signal is subjected to adaptive rearrangement in an order according to the kinds of both the prediction processes, and the second rearrangement operation in which the input signal is subjected to rearrangement in a specific order, regardless of the kinds of both the prediction processes; generating intra-frame predicted values of frequency components corresponding to the decoding target block from frequency components corresponding to an already decoded block located in the vicinity of the decoding target block, by the intra-frame prediction process; generating frequency components corresponding to the decoding target block on the basis of the input signal after the rearrangement and the intra-frame predicted values; performing inverse frequency transformation to the frequency components corresponding to the decoding target block to generate one of an image signal corresponding to the decoding target block and a difference signal corresponding to the same block; and adding, to the difference signal corresponding to the decoding target block, inter-frame predicted values of an image signal of the decoding target block, which are generated from an image signal corresponding to an already decoded display screen different from a display screen including the decoding target block by the inter-frame prediction process, thereby generating an image signal corresponding to the decoding target block.
Thus, in decoding, switching is performed, on the basis of flag information indicating switching of rearrangement, which information is input together with an input signal of a decoding target block to be subjected to decoding that is obtained by coding various frequency components which have been subjected to an inter-frame prediction process and an intra-frame prediction process in a prescribed order, between the first rearrangement operation in which the input signal is adaptively rearranged in an order according to the kinds of both the prediction processes, and the second rearrangement operation in which the input signal is rearranged in a specific order, regardless of the kinds of both the prediction processes. Therefore, accurate and efficient decoding can be carried out to a bit stream which has been coded by selecting one of plural scans for each of intra-coded macroblocks and inter-coded macroblocks, according to a parameter concerning prediction and a scan switching signal, thereby regenerating an image signal.
According to a twenty-eighth aspect of the present invention, in the image processing method as defined in the twenty-seventh aspect of the invention, a coded interlaced image signal, which is obtained by coding an interlaced image signal block by block, is received as the coded image signal to be subjected to decoding; in the first rearrangement operation, concerning an inter-coded block in which frequency components obtained by frequency transformation of the interlaced image signal correspond to inter-frame difference values of a coding target block, the frequency components to which the processing order from the side of low-frequency components toward the side of high-frequency components has been uniformly set so that the components arranged along a horizontal direction of a display screen and the components arranged along a vertical direction have uniform priorities, are rearranged according to the processing order which has been uniformly set; and concerning an intra-coded block in which frequency components obtained by frequency transformation of the interlaced image signal correspond to an image signal of a coding target block, the frequency components to which the processing order from the side of low-frequency components toward the side of high-frequency components has been adaptively set according to the kind of the intra-frame prediction process, are rearranged according to the processing order which has been adaptively set; and in the second rearrangement operation, concerning both the inter-coded block and intra-coded block, the frequency components to which the processing order from the side of low-frequency components toward the side of high-frequency components has been set so that the components arranged along a vertical direction of a display screen have priority over the components arranged along a horizontal direction, are rearranged according to the processing order which has been set with a priority given to a vertical direction.
Thus, in decoding, switching is performed, on the basis of flag information indicating switching of rearrangement, which information is input together with an input signal of a decoding target block to be subjected to decoding that is obtained by coding various frequency components which have been subjected to an inter-frame prediction process and an intra-frame prediction process in a prescribed order, between the first rearrangement operation in which the input signal is adaptively rearranged in an order according to the kinds of both the prediction processes, and the second rearrangement operation in which the input signal is rearranged in a specific order, regardless of the kinds of both the prediction processes. Therefore, accurate and efficient decoding can be carried out to a bit stream which has been coded by selecting one of plural scans for each of intra-coded macroblocks and inter-coded macroblocks, according to a parameter concerning prediction and a scan switching signal, thereby regenerating an image signal.
According to a twenty-ninth aspect of the present invention, an image processing apparatus for dividing an input digital image signal into plural image signals corresponding to plural blocks constituting a single display screen, and performing block-by-block coding of the image signals of the respective blocks, comprises a blocking unit for blocking the digital image signal correspondingly to the respective blocks, frame by frame or field by field, which is used as a processing unit of frequency transformation, and outputting the blocked image signal and frequency transformation type information indicating the processing unit of frequency transformation; inter-frame prediction means for performing inter-frame prediction to the blocked image signal to output inter-frame prediction data corresponding to inter-frame difference values between the image signal of each block and inter-frame predicted values of the image signal, and outputting inter-frame prediction information concerning the generating process of the inter-frame predicted values; intra-frame prediction means for generating intra-frame predicted values of inter-frame prediction data corresponding to a coding target block from inter-frame prediction data corresponding to an already coded block located in the vicinity of the coding target block, outputting intra-frame difference values between the inter-frame prediction data and the intra-frame predicted values, and outputting intra-frame prediction information concerning the kind of the generating process of the intra-frame predicted values; scanning means including plural scanners having different orders of rearrangement, and each being selected by a selecting signal and rearranging the intra-frame difference values, the scanning means selecting a scanner to be used for rearranging the intra-frame difference values, according to the inter-frame prediction information and a scan changing signal which is generated outside/inside a system; and a variable-length coding unit for performing variable-length coding to the intra-frame difference values after the rearrangement; and said scanning means being constructed so that switching is performed, on the basis of the scan changing signal, between the first order setting operation in which a coding order is adaptively set to the intra-frame difference values corresponding to the coding target block, according to the kinds of both the prediction processes, and the second order setting operation in which a specific coding order is set thereto, regardless of the kinds of both the prediction processes.
Thus, in coding, switching is performed, on the basis of flag information indicating switching of order setting, between the first order setting operation in which a processing order for coding is adaptively set to intra-frame difference values between frequency components of a coding target block and intra-frame predicted values of the frequency components, according to the kinds of inter-frame prediction and intra-frame prediction processes, and the second order setting operation in which a specific processing order for coding is set thereto, regardless of the kinds of both the prediction processes. Therefore, in inter coding of an interlaced image in which inter-coded macroblocks and intra-coded macroblocks having different frequency component distributions coexist, a run length is still more increased, thereby improving coding efficiency. In addition, in inter coding of a specific progressive image in which inter-coded macroblocks and intra-coded macroblocks having different frequency component distributions coexist, the same effect is obtained.
According to a thirtieth aspect of the present invention, in the image processing apparatus as defined in the twenty-ninth aspect of the invention, said inter-frame prediction means comprises a first adder for subtracting inter-frame predicted values of the blocked image signal from the blocked image signal to output a difference signal; a frequency transformation unit for performing block-by-block frequency transformation to the difference signal to output frequency components corresponding to the difference signal of each block; a quantization unit for quantizing the frequency components to output quantized values corresponding to the difference signal of each block as the inter-frame prediction data; an inverse quantization unit for inverse-quantizing the quantized values to output the frequency components corresponding to the difference signal of each block; an inverse frequency transformation unit for performing inverse frequency transformation to the output of the inverse quantization unit to output the difference signal of each block; a second adder for adding the inter-frame predicted values to the output of the inverse frequency transformation unit, and storing the result of the addition in a frame memory, as an image signal of an already coded block as a constituent of an already coded display screen; and an inter-frame predictor for generating the inter-frame predicted values on the basis of the image signal of each block and an image signal of an already coded block which is stored in the frame memory, and outputting the inter-frame predicted values and inter-frame prediction information concerning the generating process of the inter-frame predicted values; and said intra-frame prediction means comprises an intra-frame predictor for generating intra-frame predicted values of quantized values corresponding to a coding target block from quantized values corresponding to an already coded block located in the vicinity of the coding target block, and outputting the intra-frame predicted values and intra-frame prediction information concerning the kind of the generating process of the intra-frame predicted values; a third adder for subtracting the intra-frame predicted values from the quantized values corresponding to the coding target block to output intra-frame difference values; and a fourth adder for adding the intra-frame predicted values to the difference values to output the result of the addition as quantized values corresponding to an already coded block.
Thus, in coding, switching is performed, on the basis of flag information indicating switching of order setting, between the first order setting operation in which a processing order for coding is adaptively set to intra-frame difference values between frequency components of a coding target block and intra-frame predicted values of the frequency components, according to the kinds of inter-frame prediction and intra-frame prediction processes, and the second order setting operation in which a specific processing order for coding is set thereto, regardless of the kinds of both the prediction processes. Therefore, in inter coding of an interlaced image in which inter-coded macroblocks and intra-coded macroblocks having different frequency component distributions coexist, a run length is still more increased, thereby improving coding efficiency. In addition, in inter coding of a specific progressive image in which inter-coded macroblocks and intra-coded macroblocks having different frequency component distributions coexist, the same effect is obtained.
According to a thirty-first aspect of the present invention, an image processing apparatus for performing block-by-block decoding of a coded image signal that is obtained by performing a coding process including frequency transformation to a digital image signal, for each of blocks constituting a single display screen, comprises a variable-length decoding unit for performing variable-length decoding to a coded string that is obtained by performing inter-frame prediction, intra-frame prediction, frequency transformation, quantization, rearrangement, and variable-length coding to an image signal corresponding to each block; inverse scanning means including plural inverse scanners having different orders of rearrangement, and each rearranging quantized values which have been rearranged in coding so that the order of the quantized values is returned to the order before the rearrangement, the inverse scanning means selecting an inverse scanner to be used for rearranging the quantized values, according to a scan changing signal which is generated outside/inside a system, and inter-frame prediction information indicating the kind of inter-frame prediction and intra-frame prediction information indicating the kind of intra-frame prediction in coding; intra-frame prediction means for generating intra-frame predicted values of quantized values corresponding to a decoding target block from quantized values corresponding to an already decoded block located in the vicinity of the decoding target block, according to the intra-frame prediction information, and outputting the result of addition between the output of the inverse scanning means and the intra-frame predicted values; inter-frame prediction means for performing inter-frame prediction to the output of the intra-frame prediction means on the basis of the inter-frame prediction information, to generate an image signal corresponding to each block; and an inverse blocking unit for inverse-blocking the image signals of the respective blocks according to frequency transformation type information indicating a processing unit of frequency transformation in coding, to output a digital image signal; and said inverse scanning means being constructed so that switching is performed, on the basis of flag information indicating switching of rearrangement, which information is input together with an input signal of the decoding target block that is obtained by coding various frequency components which have been subjected to the inter-frame prediction process and the intra-frame prediction process in a prescribed order, between the first rearrangement operation in which the input signal is subjected to adaptive rearrangement in an order according to the kinds of both the prediction processes, and the second rearrangement operation in which the input signal is subjected to rearrangement in a specific order, regardless of the kinds of both the prediction processes.
Thus, in decoding, switching is performed, on the basis of flag information indicating switching of rearrangement, which information is input together with an input signal of a decoding target block to be subjected to decoding that is obtained by coding various frequency components which have been subjected to an inter-frame prediction process and an intra-frame prediction process in a prescribed order, between the first rearrangement operation in which the input signal is adaptively rearranged in an order according to the kinds of both the prediction processes, and the second rearrangement operation in which the input signal is rearranged in a specific order, regardless of the kinds of both the prediction processes. Therefore, accurate and efficient decoding can be carried out to a bit stream which has been coded by selecting one of plural scans for each of intra-coded macroblocks and inter-coded macroblocks, according to a parameter concerning prediction and a scan switching signal, thereby regenerating an image signal.
According to a thirty-second aspect of the present invention, in the image processing apparatus as defined in the thirty-first aspect of the invention, said intra-frame prediction means comprises an intra-frame predictor for generating intra-frame predicted values of quantized values corresponding to a decoding target block from quantized values corresponding to an already decoded block located in the vicinity of the decoding target block, according to intra-frame prediction information; and a first adder for adding the intra-frame predicted values to the output of the selected inverse scanner; and said inter-frame prediction means comprises an inverse quantization unit for inverse-quantizing the output of the first adder to output frequency components of a difference signal corresponding to each block; an inverse frequency transformation unit for performing inverse frequency transformation to the frequency components to output a difference signal corresponding to each block; a second adder for adding inter-frame predicted values of an image signal corresponding to each block to the difference signal to output an image signal corresponding to each block; a frame memory for storing the output of the second adder, as an image signal of an already decoded block as a constituent of an already decoded display screen; and an inter-frame predictor for generating the inter-frame predicted values on the basis of inter-frame prediction information and an image signal of an already coded block.
Thus, in decoding, switching is performed, on the basis of flag information indicating switching of rearrangement, which information is input together with an input signal of a decoding target block to be subjected to decoding that is obtained by coding various frequency components which have been subjected to an inter-frame prediction process and an intra-frame prediction process in a prescribed order, between the first rearrangement operation in which the input signal is adaptively rearranged in an order according to the kinds of both the prediction processes, and the second rearrangement operation in which the input signal is rearranged in a specific order, regardless of the kinds of both the prediction processes. Therefore, accurate and efficient decoding can be carried out to a bit stream which has been coded by selecting one of plural scans for each of intra-coded macroblocks and inter-coded macroblocks, according to a parameter concerning prediction and a scan switching signal, thereby regenerating an image signal.
According to a thirty-third aspect of the present invention, a data recording medium contains an image processing program, which makes a computer execute image processing in the image processing method defined in any of the first to eighth, thirteenth to eighteenth, twenty-fifth and twenty-seventh aspects. Therefore, the same effect as in any of these aspects is obtained.